SU1668029A1 - For centrifugal casting of bimetallic workrolls - Google Patents

Abstract

The invention relates to a foundry, in particular, to methods for producing cast bimetallic rolls. The aim of the invention is to obtain a more uniform in depth working layer of hardness and wear resistance of the metal. The powdery material in the amount of 0.05-0.25% by weight of the metal of the working layer is introduced in parts proportional to the increment of hardness of the working layer. In this case, the input of the first part is made after pouring 20-25% of the metal of the working layer, and ultradisperse powders of carbides and / or carbonitrides of alloying elements reducing carbon activity in iron-carbon alloys are used as the powder material.

Description

AND

This invention relates to a foundry, in particular, to methods for producing cast bimetallic rolls.

The aim of the invention is to obtain a more uniform in depth working layer of hardness and wear resistance of the metal.

The powdery material in the amount of 0.05–0 25% by weight of the metal of the working layer is introduced in parts proportional to the required increment of the hardness of the working layer, while the introduction of the first part is done after pouring 20–25% of the metal of the working layer and the powder powder powders (UDP) of carbides and / or carbonitrides of alloying elements lowering carbon activity in iron-carbon alloys

The supply of powdered material in parts is necessary in order to ensure an increase in the number of UDP particles and a proportionally increasing change in hardness over the depth of the working layer.

The indicated limits of the amount of pruned UDP are associated with a change in hardness over the depth of the working layer, which is in the range of 0.75 - 2.5 units of Brinel per millimeter, calculated from the roll surface. When entering the UDP in an amount less than 0.05% by weight of the metal of the working layer, no significant effect on hardness and wear resistance was detected. When entering the UDP in an amount greater than 0.25% by weight of the metal of the working layer, no active interaction is provided to the working layer.

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particles of UDP with liquid metal and fusing them.

Entering the first part of the UDP after pouring 20-25% of the metal of the working layer is due to the fact that the surface layers of the working layer crystallize at high speed, have high hardness and provide hardness the same as in the surface layer. Therefore, the input of the first part of the UDP before pouring 20% of the metal of the working layer is not needed, and the introduction of the UDP after pouring more than 25% of the metal of the working layer violates the uniformity of the working layer.

The use of UDP as a powdered material ensures the formation of a large amount of carbide and carbonitride particles evenly distributed throughout the metal, thereby changing the microhardness of cementite and austenite in the working layer structure, as well as the hardness and wear resistance of the material of the working layer. The need to use UDP due to the high rate of crystallization of the metal in the working layer of the rolls, this helps to increase the number of grains and reduce their size as the primary phase - austenite, and eutectic.

The use of carbides and carbonitrides is due to the production in the structure of the working layer of uniformly distributed particles with increased hardness and stability at high temperatures. The introduction of ordinary alloying elements leads to their dissolution in the liquid metal and to a qualitatively different effect on the structure as compared with carbides and carbonitrides.

PRI me R. Under identical conditions of the LZPV plant, a comparative analysis of the proposed and known methods was carried out.

On a centrifugal machine with a horizontal axis of rotation, the MCVR-1 model cast two-layer billet rolls with dimensions: outer diameter 620 mm, inner 230 mm, length 680 mm. The working layer with a thickness of 80 mm is cast from wear-resistant white cast iron, the inner layer with a thickness of 100 mm is made from gray cast iron.

After casting, 18,29,23,25 and 28% of the metal of the working layer in

A filling funnel under the stream of metal is injected with UDP in each case, respectively, of iron carbide, vanadium carbide, chromium carbonitride, manganese carbonitride, and aluminum carbide in an amount of 0.02, 0.05,

0.15, 0.25, 0.28% by weight of the metal of the working layer. By a known method simultaneously with the pouring of the metal serves iron powder in an amount of 4% by weight of the workpiece, and 8% by weight of the injected powder

introduced by pouring the working layer.

The obtained results on the decrease in hardness per 1 mm of the working layer in each case, respectively, 0,260; 0.10; 0.08; 0.05 units HB In the fifth example, receive

rejection due to the presence of microporosity in the working layer (non-fusion of UDP particles with metal). According to a known method, the decrease in hardness over the depth of the working layer is 0.275 units. HB for 1 mm.

Claims (1)

The invention The method of centrifugal casting bimetallic rolls, including sequential pouring into a rotating around the horizontal axis, the mold of the metal of the working and inner layers with the supply of powdered material to the metal of the working layer, characterized in that, in order to increase the more uniform over the depth of the working layer of hardness and wear resistance of the metal, the powdery material in the amount of 0.05-0.25% of the mass of the metal of the working layer is introduced in parts until the creation of hardness over the depth of the working a layer in the range of 0.90-0.99 of the surface hardness, with the introduction of the first part after pouring 20-25% of the metal of the working layer, and ultrafine powders of carbides and / or carbonitrides of carbon alloying elements are used as the powder material in iron-carbon alloys.